Assessment of acetylcholinesterase activity using indoxylacetate and comparison with the standard Ellman's method

Effect of naringin on sodium fluoride‑induced neurobehavioral deficits in Wistar rats

There is a lack of treatment for the detrimental effects of fluorosis. Sodium fluoride at a concentration of 10 ppm induces stress, depression and memory impairment in adult Wistar rats. Naringin, a flavanone glycoside isolated from citrus fruits such as lemons and oranges, possesses anti-inflammatory, antioxidant and neuroprotective properties; therefore, it was used for treatment of fluoride induced toxicity in the present study. Adult Wistar rats were divided into eight groups (n=8). The normal control (NOR) group was provided with normal tap water. The sodium fluoride (FLU)10 group received water containing 10 ppm sodium fluoride for 60 days. The treatment groups (FLU10NAR100 and FLU10NAR50) received drinking water with 10 ppm sodium fluoride ad libitum along with Naringin 100 and 50 mg/kg body weight (bw) per oral gavage, respectively. The NAR100 and NAR50 groups received Naringin 100 and 50 mg/kg bw. The PRONAR100 and PRONAR50 groups received Naringin 100 and 50 mg/kg bw for the first 15 days and then subsequently received FLU10 ppm for 60 days (total of 75 days). All animals were subjected to behavioural tests consisting of the open field test (OFT), forced swim test (FST) and novel object recognition test (NORT). After euthanasia, the hippocampus and prefrontal cortex were stained with Cresyl violet. To measure the oxidative stress caused by fluoride and its effect on antioxidant levels, estimation of reduced glutathione (GSH) by Ellman's method, lipid peroxidation (LPO) measured in terms of the MDA:thiobarbituric acid reaction and catalase was performed. To evaluate the effect of fluoride on activity of acetylcholine, estimation of acetylcholinesterase (AChE) by Ellman's method was performed. In NORT and FST, significant changes (P<0.05) were present in the FLU10NAR100 and FLU10NAR50 groups compared with the FLU10 group, showing recovery from memory deficit and depression. The OFT results were insignificant. The LPO was reduced in all the other groups except the FLU10 group, with statistically significant changes. Catalase activity was significantly lower in FLU10 as compared with the NAR100, NAR50, PRONAR100 and PRONAR50 groups. GSH and AChE activities did not show significant changes as compared with the FLU10 group. The CA3 and prefrontal cortex viable and degenerated neuron count in the FLU10 group were insignificant compared with all other groups, except for the NAR100 and NAR50 groups. Thus, Naringin can be a useful drug to avoid the neurological effects of fluoride.

Hydrogel-involved portable colorimetric sensor based on oxidase mimic Fe/Co-NC for acetylcholinesterase detection and pesticides inhibition assessment

Herein, we synthesized a novel N-doped carbon layer encapsulated Fe/Co bimetallic nanoparticles (Fe/Co-NC), which exhibited superior oxidase-like activity due to the facilitation of electron penetration and the formation of metal-nitrogen active sites. Fe/Co-NC could catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) to blue oxTMB. Acetylcholinesterase (AChE) could catalyze the hydrolysis of thioacetylcholine to produce reducing thiocholine, which prevented TMB from oxidation. Thus, a portable hydrogel colorimetric sensor was developed for on-site and visual monitoring of AChE with the detection limit of 0.36 U L-1, and successfully applied to detect AChE in human erythrocyte samples. Furthermore, this platform was used to investigate the inhibition of triazophos on AChE activity.

Antinociceptive Analysis of Natural Monoterpenes Eugenol, Menthol, Carvacrol and Thymol in a Zebrafish Larval Model

In the last decade, a considerable number of studies have broadened our knowledge of the nociceptive mechanisms of pain, a global health problem in both humans and animals. The use of herbal compounds such as eugenol, menthol, thymol, and carvacrol as analgesic agents has accompanied the growing interest in this area, offering a possible solution for this complex problem. Here, we aimed to explore how these natural substances-at three different concentrations (2, 5 and 10 mg/L)-affect the pain responses in zebrafish (Danio rerio) larvae exposed to 0.05% acetic acid (AA) for 1 min. By analysing the activity of acetylcholinesterase (AChE), 5'-ectonucleotidase and NTPDases, as well as aversion and exploratory behaviours, it was observed that that although all substances were effective in counteracting the pain stimulus, the concentration range within which they do so might be very limited. Eugenol, despite its acknowledged properties in fish anaesthesia, failed to alleviate the pain stimulus at low concentrations. Contrastingly, menthol exhibited the most promising results at the lowest concentrations tested. Overall, it is concluded that menthol might be a good analgesic for this species, qualifying it as a substance of interest for prospective studies.

Urine Test Strip Quantitative Assay with a Smartphone Camera

Urine test strips for urinalysis are a common diagnostic tool with minimal costs and are used in various situations including homecare and hospitalization. The coloration scaled by the naked eye is simple, but it is suitable for semiquantitative analysis only. In this paper, a colorimetric assay is developed based on a smartphone digital camera and urine test strips. Assays of pH, albumin, glucose, and lipase activity were performed as a tool for the diagnosis of aciduria, alkaluria, glycosuria, proteinuria, and leukocyturia. The RGB color channels were analyzed in the colorimetric assay, and the assay exerted good sensitivity, and all the particular diagnoses proved to be reliable. The limits of detection for glucose (0.11 mmol/L), albumin (0.15 g/L), and lipase (2.50 U/μL) were low enough to cover the expected physiological concentration, and the range for pH was also satisfactory. The urine test strips with a camera as an output detector proved applicability to spiked urine samples, and the results were also well in comparison to the standard assays which confirms the practical relevance of the presented findings.

Organophosphate Detoxification and Acetylcholinesterase Reactivation Triggered by Zeolitic Imidazolate Framework Structural Degradation

Organophosphate (OP) toxicity is related to inhibition of acetylcholinesterase (AChE) activity, which plays a key role in the neurotransmission process. In this work, we report the ability of different zinc zeolitic imidazolate frameworks (ZIFs) to behave as potential antidotes against OP poisoning. The Zn-L coordination bond (L = purine, benzimidazole, imidazole, or 2-methylimidazole) is sensitive to the G-type nerve agent model compounds diisopropylfluorophosphate (DIFP) and diisopropylchlorophosphate, leading to P-X (X = F or Cl) bond breakdown into nontoxic diisopropylphosphate. P-X hydrolysis is accompanied by ZIF structural degradation (Zn-imidazolate bond hydrolysis), with the concomitant release of the imidazolate linkers and zinc ions representing up to 95% of ZIF particle dissolution. The delivered imidazolate nucleophilic attack on the OP@AChE adduct gives rise to the recovery of AChE enzymatic function. P-X bond breakdown, ZIF structural degradation, and AChE reactivation are dependent on imidazolate linker nucleophilicity, framework topology, and particle size. The best performance is obtained for 20 nm nanoparticles (NPs) of Zn(2-methylimidazolate)2 (sod ZIF-8) exhibiting a DIFP degradation half-life of 2.6 min and full recovery of AChE activity within 1 h. 20 nm sod ZIF-8 NPs are not neurotoxic, as proven by in vitro neuroblastoma cell culture viability tests.

A novel Zebrafish model of Alzheimer's disease by Aluminium chloride; involving nitro-oxidative stress, neuroinflammation and cholinergic pathway

Alzheimer's disease (AD) is the most common form of dementia and is a progressive neurodegenerative disorder of the brain. Most AD experimental animal models are pharmacological or transgenic in origin. The existing pharmacological approaches for developing AD are poorly developed and most of them fail to replicate the complete characteristics of disease pathology. Developing a cost-effective and reliable experimental animal model will meet this research gap. Zebrafish (ZF) are progressively emerging as a powerful drug discovery disease model to evaluate central nervous system (CNS) disorders due to their homologous similarities to humans as well as cost-effectiveness. The present research is conceptualized to develop and evaluate a reliable ZF AD model using aluminum chloride (AlCl3). Chronic exposure of 0.04 mM of AlCl3 for 28 days increased the expression of amyloid-β, phosphorylated tau protein and senile plaque development in the ZF brain. The observed changes were associated with learning and memory impairment. Furthermore, decreased brain-derived neurotrophic factor (BDNF) level and elevated oxidative stress indices, pro-inflammatory cytokines levels and acetylcholine esterase (AChE) activity was observed upon exposure to AlCl3 in the ZF brain. Chronic exposure to 0.04 mM of AlCl3 would be a cost-effective ZF AD model for pharmacological screening and may also be used to unravel the molecular mechanism underlying the neuropathology of the disease.

In vitro culture of muscle cells derived from myofascial trigger points

OBJECTIVE

To examine for the in vitro existence of contractile nodules on the taut band of muscle fibers where myofascial trigger points (MTrPs) are located (using cell culture).

METHODS

Sixteen male Sprague-Dawley rats (7 weeks old) were randomly divided into experimental and control groups. A blunt striking injury and eccentric exercise were applied to the gastrocnemius muscle of rats in the experimental group once a week for 8 weeks to establish an MTrP model. Subsequently, the rats were reared normally and rested for 4 weeks. After modeling, the skeletal muscles at the MTrPs (and non-MTrPs at the same anatomical position) were extracted from the two groups of rats for in vitro cell culture experiments of single muscle fibers. Potential contractile nodules in the MTrP group were exposed to different concentrations of acetylcholinesterase, whereas non-MTrP cells were exposed to acetylcholine. The morphological changes of muscle cells in each group were observed.

RESULTS

By culturing MTrP cells in vitro, large contractile nodules remained in single MTrP muscle fibers, whereas some contractile nodules were twisted and deformed. After the addition of different acetylcholinesterase concentrations, no obvious morphological changes were observed in the contractile nodules in the MTrP group. After the non-MTrP cells were exposed to different acetylcholine concentrations, no significant morphological changes were observed in the single muscle fibers.

CONCLUSION

MTrP cells can continue to maintain contractile morphology in vitro, but whether the recovery of such contractile nodules is related to acetylcholine remains uncertain.

Stimulation of Hemolysis and Eryptosis by β-Caryophyllene Oxide

BACKGROUND

Eryptosis stimulated by anticancer drugs can lead to anemia in patients. β-caryophyllene oxide (CPO) is an anticancer sesquiterpene present in various plants; however, its effect on the structure and function of human red blood cells (RBCs) remains unexplored. The aim of this study was to investigate the hemolytic and eryptotic activities and underlying molecular mechanisms of CPO in human RBCs.

METHODS

Cells were treated with 10-100 μM of CPO for 24 h at 37 °C, and hemolysis, LDH, AST, and AChE activities were photometrically assayed. Flow cytometry was employed to determine changes in cell volume from FSC, phosphatidylserine (PS) externalization by annexin-V-FITC, intracellular calcium by Fluo4/AM, and oxidative stress by 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA). Cells were also cotreated with CPO and specific signaling inhibitors and antihemolytic agents. Furthermore, whole blood was exposed to CPO to assess its toxicity to other peripheral blood cells.

RESULTS

CPO induced concentration-responsive hemolysis with LDH and AST leakage, in addition to PS exposure, cell shrinkage, Ca2+ accumulation, oxidative stress, and reduced AChE activity. The toxicity of CPO was ameliorated by D4476, staurosporin, and necrosulfonamide. ATP and PEG 8000 protected the cells from hemolysis, while urea and isotonic sucrose had opposite effects.

CONCLUSIONS

CPO stimulates hemolysis and eryptosis through energy depletion, Ca2+ buildup, oxidative stress, and the signaling mediators casein kinase 1α, protein kinase C, and mixed lineage kinase domain-like pseudokinase. Development of CPO as an anticancer therapeutic must be approached with prudence to mitigate adverse effects on RBCs using eryptosis inhibitors, Ca2+ channel blockers, and antioxidants.

Cholinesterase Inhibitory and Anti-Inflammatory Activity of the Naphtho- and Thienobenzo-Triazole Photoproducts: Experimental and Computational Study

New 1,2,3-triazolo(thieno)stilbenes were synthesized as mixtures of isomers and efficiently photochemically transformed to their corresponding substituted thienobenzo/naphtho-triazoles in high isolated yields. The resulting photoproducts were studied as acetyl- (AChE) and butyrylcholinesterase (BChE) inhibitors without or with interconnected inhibition potential of TNF-α cytokine production. The most promising anti-inflammatory activity was shown again by naphtho-triazoles, with a derivative featuring 4-pentenyl substituents exhibiting notable potential as a cholinesterase inhibitor. To identify interactions between ligands and the active site of cholinesterases, molecular docking was performed for the best potential inhibitors. Additionally, molecular dynamics simulations were employed to assess and validate the stability and flexibility of the protein-ligand complexes generated through docking.

Affordable Portable Platform for Classic Photometry and Low-Cost Determination of Cholinesterase Activity

Excessive use of pesticides could potentially harm the environment for a long time. The reason for this is that the banned pesticide is still likely to be used incorrectly. Carbofuran and other banned pesticides that remain in the environment may also have a negative effect on human beings. In order to provide a better chance for effective environmental screening, this thesis describes a prototype of a photometer tested with cholinesterase to potentially detect pesticides in the environment. The open-source portable photodetection platform uses a color-programmable red, green and blue light-emitting diode (RGB LED) as a light source and a TSL230R light frequency sensor. Acetylcholinesterase from Electrophorus electricus (AChE) with high similarity to human AChE was used for biorecognition. The Ellman method was selected as a standard method. Two analytical approaches were applied: (1) subtraction of the output values after a certain period of time and (2) comparison of the slope values of the linear trend. The optimal preincubation time for carbofuran with AChE was 7 min. The limits of detection for carbofuran were 6.3 nmol/L for the kinetic assay and 13.5 nmol/L for the endpoint assay. The paper demonstrates that the open alternative for commercial photometry is equivalent. The concept based on the OS3P/OS3P could be used as a large-scale screening system.

Acetylcholine titre regulation by non-neuronal acetylcholinesterase 1 and its putative roles in honey bee physiology

Similar to other insects, honey bees have two acetylcholinesterases (AChEs), AmAChE1 and AmAChE2. The primary catalytic enzyme for acetylcholine (ACh) hydrolysis in synapses is AmAChE2, which is predominantly expressed in neuronal tissues, whereas AmAChE1 is expressed in both neuronal and non-neuronal tissues, with limited catalytic activity. Unlike constitutively expressed AmAChE2, AmAChE1 expression is induced under stressful conditions such as heat shock and brood rearing suppression, but its role in regulating ACh titre remains unclear. In this paper, to elucidate the role of AmAChE1, the expression of AmAChE1 was suppressed via RNA interference (RNAi) in AmAChE1-induced worker bees. The ACh titre measurement following RNAi revealed that the expression of AmAChE1 downregulated the overall ACh titre in all tissues examined without altering AmAChE2 expression. Transcriptome analysis showed that AmAChE1 knockdown upregulated protein biosynthesis, cell respiration, and thermogenesis in the head. These findings suggest that AmAChE1 is involved in decreasing neuronal activity, enhancing energy conservation, and potentially extending longevity under stressful conditions via ACh titre regulation.

The Combination of Baicalein and Memantine Reduces Oxidative Stress and Protects against β-amyloid-Induced Alzheimer’s Disease in Rat Model

Alzheimer’s disease (AD) is a neuronal condition causing progressive loss of memory and cognitive dysfunction particularly in elders. An upsurge in the global old age population has led to a proportionate increase in the prevalence of AD. The current treatments for AD are symptomatic and have debilitating side effects. A literature review and current research have directed scientists to explore natural products with better safety and efficacy profiles as new treatment options for AD. Baicalein, belonging to the flavone subclass of flavonoids, has been reported for its anti-oxidant, anti-inflammatory, AChE enzyme inhibitory activity and anti-amyloid protein aggregation activity, which collectively demonstrates its benefits as a neuroprotective agent. Presently, memantine, a NMDAR antagonist, is one of the important drugs used for treatment of Alzheimer’s disease. The current study aims to investigate the effect of baicalein in combination with memantine in β-amyloid-induced AD in albino Wistar rats. Baicalein (10 mg/kg) alone, 5 mg/kg and 10 mg/kg in combination with memantine (20 mg/kg) was administered for 21 days. Treatment with baicalein in combination with memantine showed significant improvement in behavioural studies. The combination treatment decreased oxidative stress, β-amyloid plaque formation and increased the expression of brain-derived neurotrophic factor (BDNF) in the brain. From the results, it can be concluded that treatment with baicalein and memantine could be beneficial for reducing the progression of neurodegeneration in rats. Baicalein has an additive effect in combination with memantine, making it a potential option for the treatment of AD.

Effects of baicalein with memantine on aluminium chloride-induced neurotoxicity in Wistar rats

Alzheimer's disease is a progressive neurodegenerative condition. It is one of the most common 28 forms of dementia accounting for 60-80% of people suffering from dementia. There are very few medications that are approved for the treatment of Alzheimer's disease. Baicalein, belonging to the flavone subclass of flavonoids, has been reported to have a neuroprotective effect by reducing oxidative stress and neuroinflammation, inhibiting the AChE enzyme, and reducing amyloid protein aggregation and toxicity. Memantine is one of the most important drugs used for treating Alzheimer's disease. The purpose of this work was to study the effect of baicalein with memantine on aluminum chloride-induced neurotoxicity in Wistar rats. Aluminum chloride (100 mg/kg p.o.) was administered for 42 days in male Wistar rats to induce neurotoxicity. Baicalein alone (10 mg/kg) and a combination of baicalein (5 mg/kg and 10 mg/kg) with memantine (20 mg/kg) were administered for 42 days. Treatment of baicalein with memantine showed significant improvement in behavioral parameters. The combination reduced oxidative stress and the formation of β-Amyloid plaques and increased brain-derived neurotrophic factor (BDNF) expression. Based on findings, it can be concluded that treatment with baicalein and memantine may slow the progression of neurodegeneration in rats.

The neuroprotective effect of ascorbic acid against imidacloprid-induced neurotoxicity and the role of HO-1 in mice

Imidacloprid (IMI) is not only a neurotoxic agricultural pesticide but also a possible food contaminant. The aims of this study were to (1) explore the relationship between recurrent IMI administration and neuronal toxicity in mice and (2) evaluate the potential neuroprotective effect of ascorbic acid (AA), a substance with significant free radical scavenger and having property to block the inflammatory pathways. Mice were categorized as naïve controls (administered vehicles for 28 days); the IMI-treatment animal group (administered po 45-mg/kg body weight of IMI per day for 28 days); and the IMI + AA treatment animal group (administered the same IMI dose + 200 mg/kg of AA orally for 28 days). On day 28, memory losses were assessed using the Y-maze and novel target identification behavioral tests. Mice were sacrificed 24 h after the final IMI treatments, as well as hippocampus tissues, were utilized to determine histological assessments, oxidative stress biomarkers, and Heme oxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) gene expression levels. The findings demonstrated that IMI-treated mice had substantial impairment of spatial and non-spatial memory functions, as well as reduced antioxidant enzyme and acetylcholinesterase activity. The AA neuroprotective action was achieved through the suppression of the HO-1 expression as well as the stimulation of Nrf2 expression in hippocampal tissues. In summary, recurrent IMI exposure causes oxidative stress and neurotoxicity in mice, and the administration of AA significantly reduces the IMI toxicity possibly by the activation of the HO-1/Nrf2 pathway.

Cationic biopolymer decorated Asiatic Acid and Centella asiatica extract incorporated liposomes for treating early-stage Alzheimer's disease: An In-vitro and In-vivo investigation

Background: Asiatic acid (AA) is a naturally occurring triterpenoid derivative of Centella asiatica (CA) with neuroprotective effect. The study aimed to design an ideal oral drug delivery system to treat Alzheimer's disease (AD) and develop chitosan-embedded liposomes comprising an extract of CA (CLCAE) and compare them with the chitosan-coated liposomes of asiatic acid (CLAA) for oral delivery to treat the initial phases of AD.  Methods: The solvent evaporation technique was used to develop CLCAE and CLAA, optimised with the experiment's design, and was further evaluated. Results: Nuclear magnetic resonance (NMR) studies confirmed coating with chitosan. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) indicated the successful formation of CLCAE and CLAA. Differential scanning colorimetry (DSC) confirmed the drug-phospholipid complex. Furthermore, the rate of  in vitro release of CLCAE and CLAA was found to be 69.43±0.3 % and 85.3±0.3 %, respectively, in 24 h.  Ex vivo permeation of CLCAE and CLAA was found to be 48±0.3 % and 78±0.3 %, respectively. In the Alcl3-induced AD model in rats, disease progression was confirmed by Y-maze, the preliminary histopathology evaluation showed significantly higher efficacy of the prepared liposomes (CLCAE and CLAA) compared to the Centella asiatica extract (CAE) and they were found to have equivalent efficacy to the standard drug (rivastigmine tartrate). The considerable increase in pharmacodynamic parameters in terms of neuronal count in the CLAA group indicated the protective role against Alcl3 toxicity and was also confirmed by assessing acetylcholine (Ach) levels. The pharmacokinetic study, such as C _max, T _max, and area under curve (AUC) parameters, proved an increase in AA bioavailability in the form of CLAA compared to the pure AA and CLCAE forms. Conclusion: The preclinical study suggested that CLAA was found to have better stability and an ideal oral drug delivery system to treat AD.

MolPredictX: Online Biological Activity Predictions by Machine Learning Models

Here we report the development of MolPredictX, an innovate and freely accessible web interface for biological activity predictions of query molecules. MolPredictX utilizes in-house QSAR models to provide 27 qualitative predictions (active or inactive), and quantitative probabilities for bioactivity against parasitic (Trypanosoma and Leishmania), viral (Dengue, Sars-CoV and Hepatitis C), pathogenic yeast (Candida albicans), bacterial (Salmonella enterica and Escherichia coli), and Alzheimer disease enzymes. In this article, we introduce the methodology and usability of this webtool, highlighting its potential role in the development of new drugs against a variety of diseases. MolPredictX is undergoing continuous development and is freely available at https://www.molpredictx.ufpb.br/.

Photocatalytic activity of graphene oxide-TiO2 nanocomposite on dichlorvos and malathion and assessment of toxicity changes due to photodegradation

Heterogeneous photocatalysis was used for the removal of two widely used organophosphorus pesticides, dichlorvos, and malathion from water. Graphene oxide-TiO₂ nanocomposite (GOT) was synthesized and used as a photocatalyst for the removal of these pesticides. Batch studies for optimizing photocatalytic degradation and mineralization of pesticides over 80 min were conducted by varying the pH (2-10), catalyst dose (20 mg/L-200 mg/L), and initial pesticide concentration (0.5 mg/L-20 mg/L), and the irradiation source (125 W UV and visible lamp). Degradation kinetics for the pesticides were evaluated. Ellman assay was used to estimate the toxic effect of pesticides and evaluate toxicity reduction due to treatment. The highest degradation and mineralization of dichlorvos and malathion was observed at pH 6 and the optimum catalyst dose was 60 mg/L. Under UV irradiation, 80% and 90% degradation were observed for dichlorvos and malathion, respectively for 0.5 mg/L initial pesticide concentration. The photocatalytic degradation reaction followed Langmuir-Hinshelwood kinetics. A high degree of mineralization was achieved for both the pesticides. Analysis of the results revealed that the residual toxic effect after photocatalysis was primarily due to the residual parent compound. A comparative study revealed that GOT yielded better pesticide degradation compared to commercially available TiO₂ under both UV and visible irradiation.

Synthesis, Characterization, and Enzyme Inhibition Properties of 1,2,4-Triazole Bearing Azinane Analogues

Considering the importance of acetylcholine esterase (AChE, BchE) and α-glucosidase in the treatment of Alzheimer's disease and diabetes mellitus, the synthesis of novel azinane triazole-based derivatives as effective acetylcholinesterase (AchE), α-glucosidase, urease, lipoxygenase (LOX), and butyrylcholinesterase (BChE) inhibitors is described. Azinane analogue (2) was merged with 1,2,4-triazole to acquire 1-(4-toluenesulfonyl)-4-(3-mercapto-4-methyl-4H-1,2,4-triazol-5-yl) piperidine (8) through a list of intermediates including 1-(4-toluenesulfonyl)-4-(ethoxycarbonyl) piperidine (3), 1-(4-toluenesulfonyl)-4-(2-hydrazinocarbonyl)piperidine (5), and 1-(4-toluenesulfonyl)-4-[1-(methyl amino thiocarbonyl)-2-hydrazinocarbonyl]piperidine (7). The target molecules, 1-(4-toluenesulfonyl)-4-[3-(N-alkyl/phenyl/aryl-2-ethanamoyl thio)-4-methyl-4H-1,2,4-triazol-5-yl] piperidine (12a-o), were achieved through the reaction of 8 with N-alkyl/phenyl/aryl-2-bromo ethanamides (11a-o) as electrophiles. These electrophiles were accomplished by a benign reaction of alkyl/phenyl/aryl amines (9a-o) and 2-bromo ethanoyl bromide (10). The spectral study of IR, 1D-NMR, and EI-MS corroborated the synthesized compounds. Methyl phenyl and methyl phenyl-substituted derivatives 12d and 12m with IC₅₀ = 0.73 ± 0.54; 36.74 ± 1.24; 19.35 ± 1.28; 0.017 ± 0.53; and 0.038 ± 0.50 μM are found to be the most potent AChE, α-glucosidase, urease, and BChE inhibitors. The high inhibition potential of synthesized molecules against AChE, α-glucosidase, urease, and BChEenzymes inferred their role in enzyme inhibition properties.

Identifying Possible AChE Inhibitors from Drug-like Molecules via Machine Learning and Experimental Studies

Acetylcholinesterase (AChE) is one of the most important drug targets for Alzheimer's disease (AD) treatment. In this work, a machine learning model was trained to rapidly and accurately screen large chemical databases for the potential inhibitors of AChE. The obtained results were then validated via in vitro enzyme assay. Moreover, atomistic simulations including molecular docking and molecular dynamics simulations were then used to understand molecular insights into the binding process of ligands to AChE. In particular, two compounds including benzyl trifluoromethyl ketone and trifluoromethylstyryl ketone were indicated as highly potent inhibitors of AChE because they established IC₅₀ values of 0.51 and 0.33 μM, respectively. The obtained IC₅₀ of two compounds is significantly lower than that of galantamine (2.10 μM). The predicted log(BB) suggests that the compounds may be able to traverse the blood-brain barrier. A good agreement between computational and experimental studies was observed, indicating that the hybrid approach can enhance AD therapy.

A sensitive approach for screening acetylcholinesterase inhibition of water samples using ultra-performance liquid chromatography-tandem mass spectrometry

A sensitive assay was developed to evaluate inhibitory effects of aqueous solution on acetylcholinesterase (AChE) activity via measuring hydrolysis rates of acetylcholine (ACh) based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Upon having identified precursor ions and product ions of the ACh and its hydrolysis products choline (Ch), the separation chromatogram for these two analytes has been established using a 50 mm reverse-phase BEH Shield RP18 column. The total chromatographic separation time is 7 min; limits of detection (LODs) for ACh and Ch are 0.14 µg L^-1 and 0.12 µg L^-1, respectively. A simple method for inactivation of AChE and optimization of operational parameters were then sequentially performed. It was found that adjusting solution pH to 2.5 not only can terminate the enzymatic reaction but also solve band shifting and broadening caused by aqueous matrices in chromatographic separation during UPLC-MS/MS detection. Under conditions of 0.00075 U mL^-1 AChE, initial concentration of ACh at 100 µg L^-1 and 20 min observation time, IC₅₀ values of the proposed assay for chlorpyrifos-oxon, diazoxon, malaoxon, methidathion oxon, omethoate and paraoxon were 3.5 nM, 16.8 nM, 2.4 nM, 6.8 nM, 270 nM and 36.9 nM, respectively. They are 4.5-51.9 times smaller than those reported in a LC-MS based method, and >120 times lower than those obtained by the traditional Ellman method. The results suggested that, the proposed assay significantly increases the sensitivity of commercial AChE. In addition, inhibition efficiencies of three surface waters, a groundwater and four commercial brands of bottled drinking water samples on AChE activity were firstly measured using this UPLC-MS/MS based method. These water samples were proved to have different inhibitory effects on AChE activity, and the inhibition efficiencies dependent on concentrations of dissolved organic carbon (DOC) but are independent of UV absorbance at 254 nm (UV₂₅₄) values. These results indicate that the proposed method has advantages of high sensitivity over all other conventional methods. It may become a promising AChE inhibition assay for assessing toxicity of aqueous solution containing neurotoxicity contaminants such as organophosphorus pesticides (OPPs) at low levels, or used to evaluate potential inhibition effects of natural waters on AChE activity.

Interactions of human acetylcholinesterase with phenyl valerate and acetylthiocholine: Thiocholine as an enhancer of phenyl valerate esterase activity

Phenyl valerate (PV) is a neutral substrate for measuring the PVase activity of neuropathy target esterase (NTE), a key molecular event of organophosphorus-induced delayed neuropathy. This substrate has been used to discriminate and identify other proteins with esterase activity and potential targets of organophosphorus (OP) binding. A protein with PVase activity in chicken (model for delayed neurotoxicity) was identified as butyrylcholinesterase (BChE). Further studies in human BChE suggest that other sites might be involved in PVase activity. From the theoretical docking analysis, other more favorable sites for binding PV related to the Asn289 residue located far from the catalytic site ("PVsite") were deduced.In this paper, we demonstrate that acetylcholinesterase is also able to hydrolyze PV. Robust kinetic studies of interactions between substrates PV and acetylthiocholine (AtCh) were performed. The kinetics did not fit the classic competition models among substrates. While PV interacts as a competitive inhibitor in AChE activity, AtCh at low concentrations enhances PVase activity and inhibits this activity at high concentrations. Kinetic behavior suggests that the potentiation effect is caused by thiocholine released at the active site, where AtCh could act as a Trojan Horse. We conclude that the products released at the active site could play an important role in the hydrolysis reactions of different substrates in biological systems.

Fingolimod loaded niosomes attenuates sevoflurane induced cognitive impairments

Neurocognition is a severe, neurological challenge caused due to sevoflurane application for induction of anaesthesia. The plan of this study is to investigate the effect of fingolimod loaded niosomes on the cognitive impairment induced by sevoflurane. Span 40 and cholesterol were used in reverse phase evaporation techniques for the preparation of fingolimod -loaded niosomes. The positively charged niosomes were obtained by using chloride salts of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). The Fingolimod loaded niosomes has average particle size of 223.5 nm and the surface charge measured as + 8.7 ± 1.2 mV in presence of DOTAP. The Fingolimod loaded niosomes formulation shows higher entrapment efficiency. Fingolimod loaded positively charged niosomes were efficiently retained drug and increase the sustain release property. Fingolimod niosomes increases the spontaneous alternation in Y maze and reduces the escape latency in the Morris water maze test, which leads to significant (p < 0.01) improvement in spatial short-term and long-term memory. The neuronal death in the hippocampus due to the sevoflurane exposure was attenuated by fingolimod loaded niosomes, which was proved by histopathological study. It could be defined that fingolimod loaded niosomes attenuates the sevoflurane induced cognitive impairment.

An activator-induced quencher-detachment-based turn-on probe with a cationic substrate moiety for acetylcholinesterase

We report a choline ester-grafted turn-on fluorescence probe to detect acetylcholinesterase (AChE) in living cells. The AChE-mediated hydrolysis of the choline ester moiety producing carboxylate initiates the activation of the Cy5 fluorophore quenched by an intramolecular nucleophilic mercapto group. The probe has the advantages of high AChE affinity and low cytotoxicity.

Automated High-Throughput System Combining Small-Scale Synthesis with Bioassays and Reaction Screening

The Purdue Make It system is a unique automated platform capable of small-scale in situ synthesis, screening small-molecule reactions, and performing direct label-free bioassays. The platform is based on desorption electrospray ionization (DESI), an ambient ionization method that allows for minimal sample workup and is capable of accelerating reactions in secondary droplets, thus conferring unique advantages compared with other high-throughput screening technologies. By combining DESI with liquid handling robotics, the system achieves throughputs of more than 1 sample/s, handling up to 6144 samples in a single run. As little as 100 fmol/spot of analyte is required to perform both initial analysis by mass spectrometry (MS) and further MSⁿ structural characterization. The data obtained are processed using custom software so that results are easily visualized as interactive heatmaps of reaction plates based on the peak intensities of m/z values of interest. In this paper, we review the system's capabilities as described in previous publications and demonstrate its utilization in two new high-throughput campaigns: (1) the screening of 188 unique combinatorial reactions (24 reaction types, 188 unique reaction mixtures) to determine reactivity trends and (2) label-free studies of the nicotinamide N-methyltransferase enzyme directly from the bioassay buffer. The system's versatility holds promise for several future directions, including the collection of secondary droplets containing the products from successful reaction screening measurements, the development of machine learning algorithms using data collected from compound library screening, and the adaption of a variety of relevant bioassays to high-throughput MS.

Development of portable CdS QDs screen-printed carbon electrode platform for electrochemiluminescence measurements and bioanalytical applications

In this work, a portable and disposable screen-printed electrode-based platform for CdS QDs electrochemiluminescence (ECL) detection is presented. CdS QDs were synthesized in aqueous media and placed on top of carbon electrodes by drop casting. The CdS QDs spherical assemblies consisted of nanoparticles about 4 nm diameters and served as ECL sensitizers to enzymatic assays. The nanoparticles were characterized by optical techniques, TEM and XPS. Besides, the electrode modification process was optimized and further studied by SEM and confocal microscopy. The ECL emission from CdS QDs was triggered with H₂O₂ as cofactor and enzymatic assays were employed to modulate the CdS QDs ECL signal by blocking the surface or generating H₂O₂ in situ. Thiol-bearing compounds such as thiocholine generated through the hydrolysis of acetylthiocholine by acetylcholinesterase (AChE) interacted with the surface of CdS QDs thus blocking the ECL. The biosensor showed a linear range up to 5 mU mL^-1 and a detection limit of 0.73 mU mL^-1 for AChE. Moreover, the inhibition mechanism of the enzyme was studied by using 1,5-bis-(4-allyldimethylammonium-phenyl)pentan-3-one dibromide with a detection limit of 79.22 nM. Furthermore, the natural production of H₂O₂ from the oxidation of methanol by the action of alcohol oxidase was utilized to carry out the ECL process. This enzymatic assay presented a linear range up to 0.5 mg L^-1 and a detection limit of 61.46 μg L^-1 for methanol. The reported methodology shows potential applications for the development of sensitive and easy to hand biosensors and was applied to the determination of AChE and methanol in real samples.

Cholinesterase characterization and effects of the environmental contaminants chlorpyrifos and carbofuran on two species of marine crabs, Carcinus maenas and Pachygrapsus marmoratus

Among the most frequent targets for toxic effects of modern pesticides, namely organophosphates and carbamates, one may find cholinesterases (ChEs). ChEs exist in a wide variety of animals and have been used actively to discriminate among the environmental effects of different pollutant groups, including the aforementioned pesticides. This study had three purposes, namely (i) identifying the ChE forms present in tissues (eyes and walking legs muscle) of two crab species, Carcinus maenas and Pachygrapsus marmoratus; to (ii) determine the in vitro toxicological effects, and (iii) compare the sensitivity of such enzymatic forms towards commonly used anti-ChE pesticides, namely the organophosphate chlorpyrifos and the carbamate carbofuran. Our results showed that there was not a clear preference for any of the tested substrates in any of the tissues from both species. Furthermore, the ChE activity was almost completely suppressed following incubation with eserine and with the specific inhibitor BW284C51 in all tissues from both species. In vitro exposure to chlorpyrifos promoted a significant decrease in ChE activity in both species. Furthermore, the ChE activity was completely suppressed following incubation with carbofuran and chlorpyrifos. These results suggest that the major ChE forms present in tissues of both crab species show intermediate structural properties and activity patterns, halfway between classic acetylcholinesterase and pseudocholinesterases. However, the sensitivity of the found forms towards ChE inhibitors was established, and the responsiveness of such forms towards common anti-ChE chemicals was established. Both tested species seem to be promising test organisms to be used in marine and coastal scenarios of putative contaminations by anti-ChE chemicals, considering the here reported patterns of response.

Structural and Biochemical Insights into the Inhibition of Human Acetylcholinesterase by G-Series Nerve Agents and Subsequent Reactivation by HI-6

The recent use of organophosphate nerve agents in Syria, Malaysia, Russia, and the United Kingdom has reinforced the potential threat of their intentional release. These agents act through their ability to inhibit human acetylcholinesterase (hAChE; E.C. 3.1.1.7), an enzyme vital for survival. The toxicity of hAChE inhibition via G-series nerve agents has been demonstrated to vary widely depending on the G-agent used. To gain insight into this issue, the structures of hAChE inhibited by tabun, sarin, cyclosarin, soman, and GP were obtained along with the inhibition kinetics for these agents. Through this information, the role of hAChE active site plasticity in agent selectivity is revealed. With reports indicating that the efficacy of reactivators can vary based on the nerve agent inhibiting hAChE, human recombinatorially expressed hAChE was utilized to define these variations for HI-6 among various G-agents. To identify the structural underpinnings of this phenomenon, the structures of tabun, sarin, and soman-inhibited hAChE in complex with HI-6 were determined. This revealed how the presence of G-agent adducts impacts reactivator access and placement within the active site. These insights will contribute toward a path of next-generation reactivators and an improved understanding of the innate issues with the current reactivators.

Acetylcholinesterase inhibitory activity from Amaryllis belladonna growing in Chile: enzymatic and molecular docking studies

Alkaloid profiles from Amaryllis belladonna plants collected in Chile were examined by GC-MS to assess their inhibitory activity on acetylcholinesterase (AChE) using in vitro and in silico methodologies. The alkaloid extract was roughly separated by column chromatography on silica gel. AChE inhibitory activities from extracts and purified alkaloids were tested by the Ellman method and a molecular docking study was performed to assess the interaction between AChE and purified alkaloids. Sixteen alkaloids were found from hexane and chloroform extracts, and three were isolated and identified as buphanidrine, acetylcaranine and lycorine. Chloroform extract showed the greatest AChE inhibitory activity with IC₅₀ value 8.89 µg/mL, whereas buphanidrine exhibited the highest inhibitory activity, with IC₅₀ value 17.56 µg/mL. Inhibition kinetics showed that buphanidrine acts as a mixed inhibitor and molecular docking supports this inhibition mechanism. Overall, our study supports the potential use of A. belladonna as an alkaloid source with AChE inhibitory activity.

Ethephon causes reproductive malfunction in adult male mice: Histological and biochemical evidence

Ethephon (C₂H₆ClO₃P; ETP), an organophosphorus pesticide regulating plant growth, is widely used for early ripening of fruits and vegetables in agriculture. The aim of this study was to investigate the effects of ETP on histomorphometrical and biochemical parameters in mouse testicular tissue. In this study, 90 adult male mice were randomly divided into six equal groups (n = 15). The ETP was administered orally at different doses (120, 240 and 480 mg kg^-1) daily for 35 days. Untreated control, sham (received only normal saline) and neostigmine bromide-treated (positive control; 0.10 mg kg^-1 orally; once per week) groups were also considered. Following 35 days, animals were euthanized and testicle and serum samples were taken. Accordingly, blood and serum acetylcholinesterase (AChE), catalase, total antioxidant capacity (TAC) and malondialdehyde (MDA) levels as well as histomorphometrical changes of testicles were investigated. The ETP-administered animals represented a significant reduction in AChE, TAC and catalase levels and remarkable increment in MDA content. A marked reduction was also seen in the germinal epithelium height, connective tissue thickness, seminiferous tubules diameter and Leydig cell number as well as spermiogenesis and Sertoli cell indices in ETP-treated mice compared to control ones. Similar findings were found in neostigmine bromide-treated animals. In conclusion, the ETP significantly affects the serum and blood anti-oxidant statuses and results in severe histological damages both at germ and somatic cell levels, suggesting its hematotoxic and reprotoxic characteristic.

Enzymes mediating resistance to chlorpyriphos in Aphis fabae (Homoptera: Aphididae)

The black bean aphid, Aphis fabae (Homoptera: Aphididae), is a widespread pest that has more than 200 hosts in the world. Insecticide resistance (IR) due to frequent applications is the major limitation in integrated pest management programs. Biochemical resistance is a common type of IR in which the insecticide is detoxified by one or more enzymes of the pest before reaching its target site. In this study, the IR of A. fabae populations to chlorpyrifos was evaluated in two single sprayed fields (fields A and C) and one replicated spraying field (field B) in comparison with a susceptible population (field H) during 2015. After treatments, total protein content and the activity of two detoxifying enzymes, esterases (ESTs) and glutathione S-transferases (GSTs), and acetylcholinesterase (AChE) in the populations were determined. Results clearly showed higher total protein content for the field populations compared to the susceptible population. The total protein content in field B population was significantly more than other populations. The total protein contents in Field A, B and C were 2.81, 2.89 and 1.06-fold more than susceptible strain, respectively. Higher actives of enzymes were observed in fields A, B, and C populations compared to the susceptible population (field H). The highest activity of GSTs and ESTs was observed in the field B population. Taken together, the present study demonstrated a significant IR to chlorpyrifos in the sprayed populations of A. fabae that can be attributed to the higher activity of their detoxification enzymes.

Differences in larval pesticide tolerance and esterase activity across honey bee (Apis mellifera) stocks

Honey bee populations in North America are an amalgamation of diverse progenitor ecotypes experiencing varying levels of artificial selection. Genetic differences between populations can result in variable susceptibility towards environmental stressors, and here we compared pesticide tolerances across breeding stocks using a mixture of seven pesticides frequently found in colonies providing pollination services. We administered the pesticide mixture chronically to in vitro reared larvae at four concentrations of increasing Hazard Quotient (HQ, or cumulative toxicity) and measured mortality during larval development. We found that different stocks had significantly different tolerances to our pesticide mixture as indicated by their median lethal toxicity (HQ₅₀). The intensively selected Pol-Line stock exhibited the greatest pesticide sensitivity while Old World (progenitor) and putatively feral stocks were the most pesticide-tolerant. Furthermore, we found that activity of the detoxification enzyme esterase was positively correlated with pesticide tolerance when measured using two different substrate standards, and confirmed that larvae from the Pol-Line stock had generally lower esterase activity. Consistent with an increased pesticide tolerance, the Old World and putatively feral stocks had higher esterase activities. However, esterases and other detoxification enzymes (CYP450s and GSTs) were found in similar abundances across stocks, suggesting that the differences in enzyme activity we observed might arise from stock-specific single nucleotide polymorphisms or post-translational modifications causing qualitative variation in enzyme activity. These results suggest that selective breeding may inadvertently increase honey bees' sensitivity to pesticides, whereas unselected, putatively feral and Old World stocks have larvae that are more tolerant.

Optimization of reaction time for detection of organophosphorus pesticides by enzymatic inhibition assay and mathematical modeling of enzyme inhibition

Enzyme inhibition assay was used as a biomarker for detection of organophosphates pesticides in food and environmental samples. The aim of the present study was to optimize the time of enzyme-inhibitor reaction for quantitative determination of fenitrothion organophosphate based on cholinesterase inhibition. The results showed that this method provides a time-efficient, best linearity and simple assay. The effect of reaction time on the linearity relationship of the noncompetitive inhibition equation was studied. The best linearity of the assay was found at an optimum reaction time of 3.0 min, with coefficient of determination r ² of 0.9972, in the range of inhibitor concentrations from 0.016 to 2.0 μg mL^-1. The enzyme inhibition reached a plateau at 5 min by addition of pesticide in vitro and then the inhibited enzyme reactivate spontaneously and approached steady state at 20 min. A theoretical kinetic model to explain the effect of reaction time on the enzyme inhibition by addition of pesticide in vitro was derived. The higher values of coefficient of determination r ² for the predicted model and error functions of the minimum deviations suggest that this model can be used to represent the experimental data and explain the plasma cholinesterase inhibition by fenitrothion pesticide.

The multiple biological roles of the cholinesterases

It is tacitly assumed that the biological role of acetylcholinesterase is termination of synaptic transmission at cholinergic synapses. However, together with its structural homolog, butyrylcholinesterase, it is widely distributed both within and outside the nervous system, and, in many cases, the role of both enzymes remains obscure. The transient appearance of the cholinesterases in embryonic tissues is especially enigmatic. The two enzymes' extra-synaptic roles, which are known as 'non-classical' roles, are the topic of this review. Strong evidence has been presented that AChE and BChE play morphogenetic roles in a variety of eukaryotic systems, and they do so either by acting as adhesion proteins, or as trophic factors. As trophic factors, one mode of action is to directly regulate morphogenesis, such as neurite outgrowth, by poorly understood mechanisms. The other mode is by regulating levels of acetylcholine, which acts as the direct trophic factor. Alternate substrates have been sought for the cholinesterases. Quite recently, it was shown that levels of the aggression hormone, ghrelin, which also controls appetite, are regulated by butyrylcholinesterase. The rapid hydrolysis of acetylcholine by acetylcholinesterase generates high local proton concentrations. The possible biophysical and biological consequences of this effect are discussed. The biological significance of the acetylcholinesterases secreted by parasitic nematodes is reviewed, and, finally, the involvement of acetylcholinesterase in apoptosis is considered.

Inhibition of Acetylcholinesterase by Wood Creosote and Simple Phenolic Compounds

Anisakiasis is common in countries where raw or incompletely cooked marine fish are consumed. Currently, effective therapeutic methods to treat anisakiasis are unavailable. A recent study found that wood creosote inactivates the movement of Anisakis species. Essential oil of Origanum compactum containing carvacrol and thymol, which are similar to the constituents of wood creosote, was reported to inactivate Anisakis by inhibiting its acetylcholinesterase. We examined whether wood creosote can also inhibit acetylcholinesterase. We examined the effect of components of wood creosote using the same experimental method. A computer simulation experiment (molecular docking) was also performed. Here, we demonstrate that wood creosote inactivated acetylcholinesterase in a dose-dependent manner with an IC₅₀ of 0.25 mg/mL. Components of wood creosote were also tested individually: 5-methylguaiacol, p-cresol, guaiacol, o-cresol, 2,4-dimethylphenol, m-cresol, phenol and 4-methylguaiacol inactivated the enzyme with an IC₅₀ of 14.0, 5.6, 17.0, 6.3, 3.9, 10.0, 15.2 and 27.2 mM, respectively. The mechanism of acetylcholinesterase inactivation was analyzed using a computer-based molecular docking simulation, which employed a three-dimensional structure of acetylcholinesterase and above phenolic compounds as docking ligands. The simulation indicated that the phenolic compounds bind to the active site of the enzyme, thereby competitively blocking entry of the substrate acetylcholine. These findings suggest that the mechanism for the inactivation of Anisakis movement by wood creosote is due to inhibition of acetylcholinesterase needed for motor neuron activity.

Dual electrophoretically-mediated microanalysis in multiple injection mode for the simultaneous determination of acetylcholinesterase and α-glucosidase activity applied to selected polyphenols

Acetylcholinesterase (AChE) and α-glucosidase (α-glu) are key target enzymes in the search for novel strategies in the treatment of Alzheimer's disease and type II diabetes. Therefore, methods to assess the enzyme inhibition are of great value in the research field. Here is proposed a novel a dual electrophoretically-mediated microanalysis for the simultaneous determination of both enzymes' activity. In order to do so, the various solutions required for both assays were introduced in the capillary electrophoresis system using the multiple injections approach. Enzymatic kinetic parameters were tested, K_m for AChE and α-glu were 3.81 and 0.43 mmol L^-1. K_i values were 4.27 μmol L^-1 for neostigmine (an AChE inhibitor) and 0.40 mmol L^-1 for acarbose (an α-glu inhibitor). Results of IC₅₀ (concentration for 50% of inhibition) were 5.11 ± 0.47 μmol L^-1 and 0.58 ± 0,02 mmol L^-1 for neostigmine and acarbose, respectively. All parameters (except for K_i of neostigmine) were comparable with the literature, indicating a good reliability of the proposed method to evaluate these enzymes activity. Total time analysis was approximately 10 min, being possible to perform around 12 enzymatic assays per hour, with low sample and reagent consumption, thus satisfying some of the principles of green chemistry. The method was applied to evaluate 10 phenolic compounds, of wich p-coumaric acid showed the best inhibitory activity for AChE (40.14 ± 4.75% at 10 mg L^-1); and quercetin for α-glu (46.53 ± 4.90% at 10 mg L^-1).

Inhibition of Acetylcholinesterases by Stereoisomeric Organophosphorus Compounds Containing Both Thioester and p-Nitrophenyl Leaving Groups

Studies with acetylcholinesterase (AChE) inhibited by organophosphorus (OP) compounds with two chiral centers can serve as models or surrogates for understanding the rate, orientation, and postinhibitory mechanisms by the nerve agent soman that possesses dual phosphorus and carbon chiral centers. In the current approach, stereoisomers of O-methyl, [S-(succinic acid, diethyl ester), O-(4-nitrophenyl) phosphorothiolate (MSNPs) were synthesized, and the inhibition, reactivation, and aging mechanisms were studied with electric eel AChE (eeAChE) and recombinant mouse brain AChE (rmAChE). The MSNP R_PR_C isomer was the strongest inhibitor of both eeAChE and rmAChE at 8- and 24-fold greater potency, respectively, than the weakest S_PS_C isomer. eeAChE inhibited by the R_PR_C- or R_PS_C-MSNP isomer underwent spontaneous reactivation ∼10- to 20-fold faster than the enzyme inhibited by S_PR_C- and S_PS_C-MSNP, and only 4% spontaneous reactivation was observed from the S_PR_C-eeAChE adduct. Using 2-pyridine aldoxime methiodide (2-PAM) or trimedoxime (TMB-4), eeAChE inhibited by R_PR_C- or S_PR_C-MSNP reactivated up to 90% and 3- to 4-fold faster than eeAChE inhibited by the R_PS_C- or S_PS_C-MSNP isomer. Spontaneous reactivation rates for rmAChE were 1.5- to 10-fold higher following inhibition by R_PS_C- and S_PS_C-MSNPs than inhibition by either R_C isomer, a trend opposite to that found for eeAChE. Oxime reactivation of rmAChE following inhibition by R_PR_C- and S_PR_C-MSNPs was 2.5- to 5-fold faster than inhibition by R_PS_C- or S_PS_C-MSNPs. Due to structural similarities, MSNPs that phosphylate AChE with the loss of the p-nitrophenoxy (PNP) group form identical, nonreactivatable adducts to those formed from S_P-isomalathion; however, all the MSNP isomers inhibited AChE to form adducts that reactivated. Thus, MSNPs inactivate AChE via the ejection of either PNP or thiosuccinyl groups to form a combination of reactivatable and nonreactivatable adducts, and this differs from the mechanism of AChE inhibition by isomalathion.

The hydrolysis of indoxyl acetate: A versatile reaction to assay carbonic anhydrase activity by high-throughput screening

The interest in CO₂ capture and conversion by biological methodologies into various beneficial products is increased. In nature, there are enzymes, with hydration activity, which catalyze the reversible hydration of the CO₂ molecule and, thus, are of high interest for biotechnological applications. Such enzymes are carbonic anhydrases (CAs). Structural, functional and mutational studies have shown, that besides hydratase activity, CAs have exposed hydrolytic, particularly esterase activity, and importantly, both activities follow similar catalytic mechanisms in the same catalytic pocket. CAs activity measurement methods based on electrometric assays for hydration activity and nitrophenyl based esters for hydrolytic activity assays do not fulfill the requirements amenable for enzyme activity screening methods. By this study, we were aiming to develop an indigogenic assay method based on the esterase activity of CAs. The first time use of indoxyl acetate as a substrate for CA has shown promising results to gain simplicity, repeatability, and applicability to implement high-throughput screening methods.

Screening of Carbamate and Organophosphate Pesticides in Food Matrices Using an Affordable and Simple Spectrophotometric Acetylcholinesterase Assay

Carbamates (CMs) and organophosphates (OPs) are widely used pesticides with known neurotoxicity arising from the inhibition of acetylcholinesterase (AChE). When AChE is active, in vitro, it can hydrolyze certain substrates to colored products while in the presence of an inhibitor this color development is decreased. Based on this principle, an AChE assay for CM and OP compounds was optimized and validated for carbofuran, carbofuran-3-hydroxy and dichlorvos in lettuce and strawberry extracts. The analytical performance of the assay was confirmed by an accredited liquid chromatography tandem mass spectrometry (LC–MS/MS) method. The developed AChE assay achieved low limits of detection (LODs) at the part per billion (ppb) level, depending the analyte inhibitory strength, recovery rates higher than 70% and good repeatability. Moreover, the toxic unit (TU) approach was applied, for extracts containing the validated analytes, and antagonism was noticed in all cases. Overall, the developed method is rapid, simple, cost-effective and may find application as a low-cost pre-screening tool of AChE inhibitors presence. Last but not least, this study can be considered a guide on development, validation and benchmarking of bioassays in food safety, a topic, which is commonly mispresented in the available literature.

Acetylcholinesterase-catalyzed silver deposition for ultrasensitive electrochemical biosensing of organophosphorus pesticides

This work reports, for the first time, acetylcholinesterase-catalyzed silver deposition for sensitive electrochemical detection of organophosphorus pesticides.

Design, synthesis, biological evaluation and molecular docking study of novel pyridoxine–triazoles as anti-Alzheimer's agents

A series of multi-target natural product-pyridoxine based derivatives were designed, synthesized, characterized and evaluated as anti-Alzheimer agents. In vitro testing revealed the multi-functional properties of compounds such as inhibition of acetylcholinesterase (AChE), antioxidant and metal chelation. Among the series, 5i derivative was found most potent AChE inhibitor, possess antioxidant potential and chelating metal ions. Further binding interaction of 5i with AChE was studied using molecular docking, showed interaction with both PAS and CAS site of AChE. In silico predictions were also performed to predict toxicity and ADME properties of the molecule 5i and found within drug likeness range. Therefore, 5i could be a promising multi-functional compound that can be used for further development of novel drug for Alzheimer disease.

A series of multi-target natural product-pyridoxine based derivatives were designed, synthesized, characterized and evaluated as anti-Alzheimer agents. Out of all the molecules of the series, 5i was found to be best.

A Strip Biosensor with Guinea Green B and Fuchsin Basic Color Indicators on a Glass Nanofiber Carrier for the Cholinesterase Detection of Nerve Agents

This paper deals with the innovation of the Czech colorimetric biosensor Detehit designed for the simple, fast, and sensitive detection of nerve agents. The innovation is based on the use of an indicator consisting of a mixture of two triphenylmethane dyes, Guinea green B and a basic fuchsin, on a glass nanofiber filter paper carrier. The advantage of this solution is the blue-red color transition, which is much more visible than the white-yellow transition of other Detehit biosensors. The newly designed biosensor allows the users to visually detect (with the naked eye) the presence of the most significant paralytic substances (sarin, soman, cyclosarin, tabun, VX) in water at concentrations of at least 0.001 μg/mL. This biosensor design also enables one to detect these substances in air or on contaminated surfaces.